The invention relates to a fastener and a delivery instrument for joining multiple layers of thin flexible material. More particularly, the invention relates to a surgical fastener and a delivery instrument and method for joining living tissue and/or synthetic materials which may be used as a substitute for tissue.
Still more specifically, the invention relates to a system for joining large grafts to the human aorta less invasively and with substantially less blood loss than is typically experienced in this type of operation. The invention further permits the graft to be anastomosed to the aorta without temporarily stopping the flow of blood distal to the operating site. The combination of a less invasive, less traumatic, procedure provides the surgeon with more freedom in choosing the most appropriate site in which to attach the graft.
Historically, living tissue has been most commonly surgically repaired by thread, such as a suture, introduced by a pointed metal needle and tied with just enough tension to establish hemostasis, or control of bleeding, by compressing the tissue. Correct tension is established by the surgeon based on observation and. judgment derived from extensive training. Excess tension can cause necrosis (the localized death of living tissue) and eventual failure of the repair.
An alternative method of joining tissue using metal staples has evolved over the last 90 years to a point where specialized staples for both skin and internal tissue closure are in common use today. The staples., which have sharp points for penetrating tissue, are formed in place by delivery instruments which bend them to a permanent shape suitable for tissue retention. The delivery instruments include mechanisms, such as an anvil, which control to some extent the relationship between tissue and staple, including the compression necessary to control bleeding. To the extent that they do so, surgeon skill is less of a factor in successful wound closure.
For conventional surgery, the clinical results for suturing and stapling are essentially the same, but both have their disadvantages. Sutures are suitable for all types of wound closure, but require that the surgeon have adequate access to the wound site and possess the skill to choose and apply the suture correctly. Conventional staples can also be appropriate for internal use, but require that a strong, rigid anvil be placed behind the tissues to be joined. Furthermore, the application of staples requires that there be enough space for an instrument, which can produce the necessary force to form the staple against the anvil. Stapling, however, is generally faster and, as previously noted, requires a lower level of skill.
The recent development of a beneficial, less invasive technique for gall bladder removal has suggested the feasibility of other abdominal procedures, such as a bowel and hernia repair, that require the remote application of an internal fastener. As a result, less invasive instruments have been developed for both suturing and stapling remotely from the wound site by the surgeon. At the same time, patient benefit considerations are driving the development of less invasive techniques for a full range of abdominal and thoracic procedures including coronary artery bypass and valve replacement.
To date, stapling has proven to be more suitable for less invasive surgery than suturing. Instruments developed for that purpose approximately replicate the functions of staplers developed for open surgery and are approximately as easy to use. Instruments developed for less invasive suturing, on the other hand, are slow and cumbersome and do not solve the essential problem of tensioning the suture and tying the knot remotely. Sutures will find limited use in less invasive surgery but it is most likely that related wound closure problems beyond the capability of conventional staples will be solved by innovative mechanical fasteners which can more easily be remotely applied.
For instance, a new fastener has been designed for less invasive hernia repair in which a synthetic mesh is used to reinforce the repair by anchoring it to surrounding tissue. Suturing is feasible but difficult. Conventional stapling is not feasible because an anvil cannot access the distal side of the tissue. The new fastener has the shape of a coil spring with the wire sharpened at one end and has been used successfully to attach the mesh by screwing the coil through it into the tissue. This new fastener can access the wound site through a small port in the abdominal wall. This fastener, however, does not produce compression upon the synthetic and natural tissue layers and thus does not produce hemostasis because the fastener is screwed into the wound site in its natural shape. Because this fastener does not produce hemostasis, it may not be suitable for a wide range of surgical applications.
Other surgical fasteners have been fabricated from shape memory alloy. U.S. Pat. No. 4,485,816 to Krumme discloses a shape-memory surgical staple that uses an electric current to heat the staple to make it close. U.S. Pat. No. 5,002,562 to Pyka et al. discloses a fastener made from shape memory alloy that has the shape of a suturing loop in its unreformed shape. As noted above, however, sutures and staples are not always desirable for all surgical applications.
It is believed that other applications exist or will be identified for fastening layers of tissue where anvil access is not practical and where compression must be applied to the tissue to achieve hemostasis. For example, these criteria apply to the attachment of a graft more or less at right angles to another, larger, blood vessel (xe2x80x9cend to sidexe2x80x9d anastomosis) such as the aorta for vascular bypass purposes. The availability of a less invasive vascular bypass procedure implies a significant patient benefit. Another example is the use of the fastener in endovascular procedures to attach a graft within large vessels such as the aorta, iliac or femoral arteries to repair aneurysms and occlusions. Stents, which are currently used for this purpose, are often insufficiently compliant to prevent leakage and consequent failure of the repair. Direct fixation of the graft to the inner wall of the vessel by the fasteners described herein may overcome this inherent problem of current techniques for endovascular repair.
What is desired, therefore, is a mechanical fastener and deployment instrument that can access internal tissue through a small surgical access port or incision and that can be applied conveniently and remotely.
With respect to the aforesaid joining of grafts to a human aorta, grafts, usually synthetic, are commonly used to surgically bypass major arteries which are critically blocked by occlusive disease. These include, but are not limited to, femoral, iliac, renal and other visceral arteries. In this procedure, as practiced conventially, the graft is joined to the aorta at a convenient place (one which is surgically accessible, not calcified and reasonably close to the blockage), and connected to the diseased vessel at a point distal to the blockage. These secondary vascular connections (anastomoses) are made using conventional sutures to provide mechanical strength and control of bleeding (hemostasis). Large grafts are also used to bypass aneurysms or weaknesses in the walls, of major arteries to forestall an emergency or life threatening condition. After bypass, the diseased portion of the artery is blocked to isolate it from the stress of arterial pressure. There are problems associated with both of these bypass techniques. In general, the most difficult part of the procedure with respect to the human aorta is in making the initial connection to the wall of the aorta. In essence, a hole the size of the graft is made in the wall with the aorta temporarily blocked. The graft is then carefully sutured to the periphery of the hole. The blocking clamp is then removed and flow through the aorta is reestablished. The potential for blood loss is significant due to the large volume of blood and relatively high systolic pressure in the aorta. In addition, the need to use a blocking clamp to prevent blood loss introduces a significant strain on the heart.
There is thus a need for an instrument to deliver the graft, and a procedure for puncturing the aorta and making an anastomosis quickly and reliably through a small incision with minimal loss of blood.
Accordingly, an object of the present invention is to provide a surgical fastener that can access internal tissue through a small surgical access port or incision.
It is a further object of the present invention to provide a surgical fastener that can be applied remotely.
It is yet another object of the present invention to provide a surgical fastener that uses the superelastic properties of shape memory alloy without having to apply heat to the fastener.
It is still another object of the present invention to provide a deployment instrument that can be used to deploy the surgical fasteners of above.
A still further object of the present invention is to provide an improved instrument and method for delivering a graft to the operative site, puncturing the aorta, and making an anastomosis quickly and reliably through a small incision, and with minimal loss of blood and reduced heart strain.
These objects of the invention are achieved by a surgical fastener preferably made from a shape memory alloy that accesses internal tissue or other synthetic material through a small surgical access port or incision. After the fastener is deployed through layers of tissue, it assumes a shape that automatically applies to the layers of tissue an appropriate hemostatic compression which is relatively independent of tissue thickness. The fastener is a suitable replacement for conventional non bio-absorbable sutures and staples in certain clinical applications. Its shape, method of deployment, and low force requirements make it suitable for standard surgical procedures and especially suitable for laparoscopic and other less invasive surgery where access to the wound site is limited, including endovascular surgery. The invention is expected to be especially useful for attaching synthetic grafts to an aorta.
In accordance with a further feature of the invention, there is provided an instrument for attaching a graft to an aorta or other tubular structure. The instrument comprises a first needle assembly for breaching the aorta to provide a hole in a wall thereof, a carrier portion for insertion of an end of a tubular graft through the hole and into the aorta, arms pivotally mounted on the instrument and moveable from a position extending axially of the carrier to a position extending radially from the carrier to spread the end of the tubular graft radially outwardly from a tubular body portion of the graft to form a generally annular flange portion extending outwardly from the tubular body portion, and to support the flange portion within the aorta and around the hole therein. A second needle assembly is adapted to retain suture material (e.g., the aforementioned surgical fastener) therein and to advance the suture material into engagement with the aorta wall and the graft flange portion for suturing the graft flange portion to the aorta wall.
In accordance with a still further feature of the invention, there is provided a method for fixing a graft to an aorta or other tubular structure. The method comprises the steps of providing a graft having a tubular body portion and an annular flange portion at one end of the tubular body portion, providing an instrument for breaching the aorta, positioning the flange portion of the graft adjacent a wall of the aorta, and suturing (e.g., with the aforementioned surgical fastener) the graft flange portion to the aorta. The method includes mounting the graft in the instrument, and mounting a needle assembly, supporting suturing material, on the instrument. The method further includes operating the instrument to breach (i) the aorta to provide a hole therein, (ii) to move the graft to engage the aorta around the hole therein with the graft flange portion, (iii) to provide anvil support to the graft flange portion within the aorta, and (iv) to effect suturing of the graft flange onto the aorta around the hole in the aorta.
The above and other features of the invention, including various novel details of construction and combinations of parts and method steps will now be more particularly described with reference to the accompanying drawings and pointed out in the claims. It will be understood that the particular devices and method steps embodying the invention are shown by way of illustration only and not as limitations of the invention. The principles and features of this invention may be employed in various and numerous embodiments without departing from the scope of the invention.